The invention relates to electrical means for dividing the primary step of a stepping motor to increase the number of motor steps per revolution of the rotor of the motor. More particularly, the invention relates to such a motor step divider including means for operating class A transistor phase drivers at a reduced voltage and momentarily boosting the operational voltage for a motor phase winding when increasing driving current is applied by a driver to the winding.
In the U.S. Pat. No. 3,444,447, entitled "Multi-Phase Step Motor Control Circuits Including Means for Supplementing the Normal Energization of the Windings", there is disclosed a multi-phase driver circuit for energizing the phase windings of a stepping motor according to a switching logic program so that each phase winding is energized for a certain period and is thereafter de-energized for a certain period.
However, in such a prior art control circuit, the phases of the motor are operated either fully on or fully off, thus providing a fixed prime step for the motor. If a greater resolution for a particular stepping motor is required, it has not heretofore been possible to easily modify or otherwise control the motor to increase the number of motor steps per revolution.
Accordingly, it is an object of this invention to provide a step divider means for adjustably dividing the prime step of a stepping motor into smaller steps to achieve a greater stepping resolution.
A further object of this invention is to provide such a step divider means that will operate to apply incrementally increasing and decreasing driving current to adjacent motor phase windings to servo the rotor smoothly between adjacent motor phase positions.
Another object of the invention is to provide an apparatus for dividing the prime step of a stepping motor by a factor that may be altered by changing a wired counter preset plug and associated sine and cosine programmable read-only memories.
In the U.S. Pat. No. 3,662,245 entitled, "Controlled Circuit for Energizing the Windings of Multi-Phase Step Motors Including a Two-Level Supply Voltage", there is disclosed a control circuit for reducing the power dissipation of the phase drivers of a step motor by operating the drivers at a reduced voltage and applying a voltage boost signal to a phase winding of the motor when driving current is applied to the winding. However, such a prior art voltage boost circuit has been employed to provide a voltage boost over the entire period of energization of a phase winding and, therefore, is not appropriate for efficient operation when an incrementally increasing or decreasing phase current is employed to energize the phase windings of a motor.
Accordingly, it is a further object of the invention to provide a voltage boost means for applying an increased voltage signal to a phase winding of a stepping motor when incrementally increasing driving current is applied to the winding.
These and other objects of this invention will become apparent from a review of the detailed specification which follows and a consideration of the accompanying drawings.